Using \(\theta _{\infty }=\frac{u_{sp}}{D_{OL}}\)  and
equations (REF ), (REF ) and (REF ) we can estimate the
values of the observable in the strong field gravitational lensing.
The variation of the observables \(\theta _{\infty }\) , \(s\)  and \(r_m\) 
are plotted in figures 7-9. Note that the mass of the central object
of our galaxy is estimated to be \(4.31\times 10^6 M_\odot \)  and the
distance between the sun and the
center of galaxy is \(D_{OL}=8.5\,kpc\)  [1]}.
